Process of producing oxalic acid.



UNITED STATES PATENT OFFICE.

EMIL VON PORTHFEIM, OF PRAGUE, AUSTRIA-HUNGARY.

PROCESS OF PRODUCING OXALIC ACID.

No Drawing.

To all whom it may concern Be it known that I, EMIL voN POBTHEIM manufacturer, a subject of the Emperor o Austria-Hungary, and resident of Prague, in the Empire of Austria-Hungary, have invented certain new and useful Improvements in Processes of Producing Oxalic Acid; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

A number of methods are known for the oxidation of sugar and other carbohydrates by aid of nitric acid or nitric oxids in the presence of catalyzers; to all of these, however, there is common a very considerable drawback, namely, that of an extremely large and spontaneous'lncrease of temperature arising in the course of the initial stage.

of the process. Now -while it has indeed been claimed that such a spontaneous increase of temperature may be removed by cooling, it has actually been found that this will only take place when the experiments areconducted on a small scale, and that,

whensoever it is attempted to carry out the process on a large scale, such as work in a factory renders necessary, it proves impossible to remove by cooling the heat initially developed within the masses subjected to' the reaction. On the contrary, the temperature will, within a short time, attain such a degree as to cause the reaction to take place with the violence of an explosion, in consequence of which not only alarge portion of the sugar is oxidized to carbonic acid, but there will also suddenly arise nitrous gases in such a considerable quantity that it will be foundimpossible to deal with them satisfactorily. By means, of my invention it is possible to uniformly distribute the said sudden development of heat over any de sired length of time and thus to safely prevent the otherwise too violent reaction. What is done, is to preliminarily treat the sugar with nitrous gases in the absence of a catalyzer, before it is used for the production of oxalic acid. To this end, the dry ment of heat taking place continuously.

Specification of Letters Patent.

The increase in the temperature of the Patented Nov. 21, 1916.

. Application filed March 27, 1916.- Serial No. 86,969. i

be allowed to rise to 60 0. without impair ing the yield of oxalic acid. In order to shorten the tlme required for the aforesaid preliminary treatment, it is advisable to cause the vessel to be cooled from withouty notwithstanding the same result will be obtalned in a slightly longer period of time without going to the trouble of cooling the vessel. The sugar thus preliminarily treated 1s hereupon employed according to any one of the known methods, inthe place of the non-treated sugar, for the production of oxalic acid. I

In the course of the main-oxidizing proc-' ess,bu t little or no heat will be developed, according to whether the preliminary treat ment had or had not been'continued until the development of the heat had been completed.

The yield of oxalic acid, calculated upon the basis of the quantity of pure sugar employed, 1s .111 no way influenced by the prellmlnary treatment; in other words, it is identical with that obtained when the production of the oxalic acid is efiected without the aid of'a preliminary treatment, that is to say, on a small scale, in the laboratory, where the cooling still proves successful.

Example I5 100 parts by weight of sugar are treated wlth 100 to 200 parts by weight of gaseous N0 the temperature being maintalned at about 3040 G. by suitably selecting the velocity of the flow of gas and of quantity of nitric acid of any degree of con centratlon desired containing the aforesaid 3.6 parts by weight of water, and further, as a catalyzer,.ox1d of molybdenum or oxid of vanadium; whereupon further quantities of NO are introduced until the formation of oxalic cid is almost complete.

The wo king up of the mass is carried out in such a manner that, for example, after the expulsion of the nitrous gases by aid of air, the crystals which have formed themselves are removed from the vessel, are then separated by suction or by means of centrifugal force from the mother-liquor still are placed upon a contained in the upper part of a clinging to them; whereupon, while the latter is again made use of as a starting liquor for a fresh reaction, the crystals are cleansed by means of re-crystallization. However, by continuously passing through a strong current of air, the mixture of crystals and mother-liquor may be heated up to 50 0., in consequence of which, while, whatever portion of the carbohydrate still remaining will be oxidized to oxalic acid, the nitric acid present in the said mixture will be split into nitrous gases (which escape) and water which remains behind). As a result of the separation by centrifugal power and the recrystallization of the oxalic acid obtained in this manner, the filtrate obtained will prove to be, for all practical purposes, a solutionof the catalyzer free from all nitrogen compounds;

Example II: 100 parts by weight of sugar slightly inclined grid or the like, closed vessel, whereupon 150 to 200 parts by Weight of NO are off to the lower portion of the vessel. Upon the termination ofthis preliminary treatment, 400 parts by Weight of nitric acid of a density of 40 Be. and the required quanpassed through. The sugar is gradually liquefied and slowly flows tity of catalyzer are added to the sugar. In consequence of the presence of nitrous gases, which have been absorbed by the sugar, the reaction immediately commences and may be kept at a uniform rate with extraordinary facility, simply by cooling.

Example III: 100 parts by weight of sugar are treated with 150-200 parts by weight of gaseous NO and are then introduced into 1000 parts by Weight of a mixture of nitric acid and diluted sulfuric acid containing the catalyzer. The temperature is maintained at 50'60 C., until the reaction is completed.

What I claim is The process of producing oxalic acid from sugar and other carbohydrates by means of nitric oxids o'r nitric acid and catalyzers, which comprises subjecting the carbohydrates to a preliminary treatment with nitrous gases.

In testimony that I claim the foregoing as my invention I havesi'gned my name in presence of two subscribing witnesses.

EMIL VON PORTHEIM. 

